Step 1. From the primary side we completely drill out the plating in the via hole to isolate the hole from layer 9 while, but leave the perimeter of the surface pad and the connection to the surface pad intact.

Step 2. On secondary side we perform a control depth mill drill to expose the layer 15 ground plane. You can see the ground layer as a crescent shape in the photo.

Step 3. On secondary side solder we solder a wire to the exposed layer 15 and route the wire through the circuit board.

Step 4. We solder the opposite end of the wire to the via pad on the primary side.

Step 5. On the secondary we side fill and seal the exposed plane and attached wire connection using high strength epoxy tinted with a color agent.

Step 6. On the primary side we fill and seal the attached wire connection using high strength epoxy tinted with a color agent.

This procedure was used to modify a batch of circuit boards that had a signal error at a via hole location. A via hole on this multilayer circuit board was mistakenly connected to layer nine when it should have been connected to layer 15.

This is genuine micro-surgery, but in the hands of skilled and trained technicians, it can be done with neatly and reliably.

Here is how we do it.

From the primary side we completely drill out the plating in the via hole to isolate the hole from layer 9 while, but leave the perimeter of the surface pad and the connection to the surface pad intact.

On secondary side we perform a control depth mill drill to expose the layer 15 ground plane. You can see the ground layer as a crescent shape in the photo.

On secondary side solder we solder a wire to the exposed layer 15 and route the wire through the circuit board.

We solder the opposite end of the wire to the via pad on the primary side.

On the secondary we side fill and seal the exposed plane and attached wire connection using high strength epoxy tinted with a color agent.

On the primary side we fill and seal the attached wire connection using high strength epoxy tinted with a color agent.

This would a very challenging, if not impossible task for most, but not for the properly equipped and skilled technicians. Another hearty handshake and a pat on the back to the super techs at Circuit Technology Center.

Several members of the Circuit Technology Center team contributed to this feature story.

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Customer Comments"We were certain the circuit board we sent to you were beyond repair, but we sent them anyway. They came back, we tested them, and they all functioned perfectly. Job well done!" A.Z. Guadalupe, Mexico